Process for the manufacture of ketone derivatives

ABSTRACT

The nitrosation of Alpha -nitrocycloalkanones with alkyl nitrites, nitrogen oxides or nitrosyl halides is advantageously carried out utilizing liquid sulfur dioxide as a reaction solvent. Most advantageously, a strong acid catalyst is also present.

United States Patent Fuhrmann et al.

[ Dec. 30, 1975 PROCESS FOR THE MANUFACTURE OF KETONE DERIVATIVES Inventors: Robert Fuhrm'ann, Morris Plains;

Stylianos Sifniades, Madison; Allen Abraham Tunick, Denville, all of Assignee: Allied Chemical Corporation, New

York, N.Y.

Filed: June 20, 1973 Appl. No.: 371,908

Related US. Application Data Division of Ser. No. 237,886, March 24, 1972, Pat. No. 3,758,851, which is a continuation-in-part of Ser. No. 852,881, Aug. 25, 1969, abandoned.

US. Cl. 260/566 A; 424/327 Int. Cl. C07C 131/02 Field of Search 260/566 A OTHER PUBLICATIONS Morrison et al., Organic Chemistry, pp. 634-635, (1962).

Primary ExaminerGerald A. Schwartz Attorney, Agent, or Firm-Arthur J. Plantamura [57] ABSTRACT The nitrosation of a-nitrocycloalkanones with,alkyl nitrites, nitrogen oxides or nitrosyl halides is advantageously carried out utilizing liquid sulfur dioxide as a reaction solvent. Most advantageously, a strong acid catalyst is also present.

9 Claims, No Drawings PROCESS FOR THE MANUFACTURE OF KETONE DERIVATIVES I This is a division of application Ser. No. 237,886, filed Nov. 24, 1972, now US. Pat. No. 3,758,851, which is a continuation in part of commonly assigned application Ser. No. 852,881 filed Aug. 25, 1969, now abandoned.

BACKGROUND OF THE INVENTION This invention relates to a process for the nitrosation of a-nitrocycloalkanones, more particularly, to the nitrosation of C to C a-nitrocycloalkanones using liquid sulfur dioxide (S as the nitrosation reaction solvent.

SUMMARY OF THE INVENTION It has now been found in accordance with the instant invention that C to C a-nitrocycloalkanones can be nitrosated in liquid'SO to afford the corresponding oz-nitro-a-oximino cycloalkanone in very high yield. All other reaction solvents tried afford significantly lower yields of product. However, we have found that the exceptionally high yields obtained in the instant process do not result merely from the use of SO as a reaction solvent, but that other reactants must be present and also that certain reaction conditions must be maintained.

Specifically, we have found that to obtain optimum yields the concentration of a-nitrocycloalkanone, hereinafter ANC, in the liquid S0 reaction solvent must be at least about wt.% and further, that there must be present at least one mole of a C to C alkanol per mole of ANC. The alkanol can be present either as such or as part of the nitrosating agent molecule as will be more fully explained hereinafter. There should also be present a strong acid catalyst. Under the aforementioned conditions, the initial nitrosation product is not the a-nitro-a'-oximino cycloalkanone, but rather a compound of limited stability which'is believed to be a a-nitro-a'-oximino hemi-ketal which is readily transformed into a ketal which is stable, and can be isolated as such or converted to the free a-nitro-d-oximino cycloalkanone. The nitrosation reaction of the instant invention can be schematically represented as follows:

with the instant inventionrThese compounds are ordinarily prepared by nitration of the corresponding ketone. Such nitration is most advantageously carried out by forming the enol acylate of the ketone by reaction of i the ketone with a carboxylic acid anhydride or with ketene, e.g., using cyclohexanone,

OCCH

acetic anhydride The enol acetate is then nitrated with a nitrating agent such as acetyl nitrate.

Suitable ketones'include any of the C to C cycloalkanones such as cyclopentanone, -hexanone,

.-heptanone, -octanone, -nonanone, -decanone, and

-dodecanone, and 4-methyl cyclohexanone.

In carrying out our nitrosation procedure the ocnitrocycloalkanone (I) is dissolved in liquid S0 The concentration of compound (I) in SO should be at least about 10 wt.%, preferably from about 10 to about wt.%, most preferably 15 to 35 wt.%. Concentrations lower than about 10 wt.% result in a significantly reduced yield of the desired product III. In addition to compound I there is dissolved in the liquid S0 nitrosating agent and C to C alkanol, ROI-I. The nitrosating agent and alkanol are preferably added portionwise to the ANC in SO solution. However, if desired although it is not preferred, the ANC in S0 can be added to the nitrosating agent and alkanol either neat or also dissolved in S0 Suitable nitrosating agents include the C to C, alkyl nitrites, nitrosyl formate, chloride, or bromide and N 0 The preferred nitrosating agent is methyl nitrite or nitrosyl chloride. From about 1.0 to L5 moles of nitrosating agent per mole of ANC should be utilized. Lesser amounts reduce the yield of product, while nitrosating ag' "nt oximino g ROH, acid hemi-ket'al 0 9 H 1) base /\C ROI! 2) acid HON=C H-NO (III) (0H wherein n 2 to 9 and R connontes a C to C alkyl greater amounts provide no improvement in yield, but

group.

As heretofore indicated, C to C a-nitrocycloalkanones are the compounds nitrosated in accordance increase the cost.

Any of the C, to C alkanols, e.g., methanol, ethanol, isopropanol, or nor t-butanol can appropriately be used. The preferred alkanol is methanol because of its cheapness and volatility. The amount of alkanol which should be added is dependent upon the nitrosating agent chosen. If a nitrosating agent other than a C to C alkyl nitrate is utilized, at least 1 mole of ROH per mole of ANC should be added. Yields of hemi-ketal are enhanced if at least about 2.0 moles of ROH per mole of ANC is used. Where a C to C alkyl nitrate is chosen as the nitrosating agent, each mole of such nitrosating agent is the effective equivalent of one mole of alkanol. Therefore if such alkyl nitrite is utilized as nitrosating agent, no ROH need be added. However, we have found that even when using an alkyl nitrite as the nitrosating agent higher yields of product are obtained when free alkanol ROH is also added. Preferably, at least about 0.5 mole of alkanol per mole of ANC is added. If the R of the alkanol ROH and of the alkyl nitrite RONO are different, a mixture of hemi-ketals may be found, however, this does not affect yield.

We have also found that the nitrosation reaction proceeds more readily and in higher yield in the presence of a strong acid catalyst. Any nonoxidizing acid having a pKa of less than about 1 is suitable such as for example, hydrochloric, hydrobromic, sulfuric, phosphoric, p-toluene sulfonic, or methane sulfonic acid. The amount of acid present in the reaction mixture is not critical but it should preferably be sufficient to provide at least about 4.0 moles of acid per mole of ANC. Because of its high volatility, hydrochloric acid is readily removed from the reaction mixture after completion of the reaction and for this reason it is preferred. The acid can be added prior to or simultaneously with the nitrosating agent, preferably prior to the nitrosating agent.

The temperature at which the solution of a-nitrocycloalkanone in S is preferably maintained during and after addition of the nitrosating agent ranges from about 30 up to +25C., most preferably 20 to +5C. Below about 30C., the nitrosation reaction proceeds ata slow rate. Above about +25C., side reactions, which reduce yield, tend to occur.

Nitrosation is ordinarily complete within from 1 to 12 hours after the nitrosating agent has been added. With other conditions remaining constant, the higher the temperature the shorter the time required for complete reaction. Completion of the nitrosation reaction can readily be ascertained by vapor phase chromatographic analysis of an aliquot of the reaction mixture if conditions are varied from those having a predetermined completion time. Ordinarily, the nitrosation reaction mixture is worked-up promptly after completion of the nitrosation reaction. Work-up is most conveniently carried out by stripping off the S0 which boils at C. at atmospheric pressure, any excess nitrosating agent and alkanol and the HCl catalyst under reduced pressure, preferably at a temperature below about 0C., leaving behind hemi-ketal as a residue. If a nonvolatile acid catalyst is used, it must be removed from the reaction mixture or neutralized prior to removal of the S0 by stripping.

As heretofore indicated, this hemi-ketal is of limited stability and will slowly decompose if left standing after evaporation of the S02. In S0 solution the hemiketal is apparently stable indefinitely and hence if desired such solutions can be retained for prolonged periods.

The hemi-ketal residue remaining after stripping off S0 acid catalyst and any unreacted nitrosating agent and alkanol is then reacted with at least 1.0 mole of C to C alkanol to afford ketal (ll). The hemi-ketal is preferably worked-up by dissolving in C to C alkanol. The hemi-ketal can be transformed directly into compound III by reaction with water although yields are somewhat lower than those obtained by the two-step reaction sequence described hereinabove. The alkanol used can be the same as or different from that initially present in the reaction mixture or a mixture of alkanols can be used. If a different alkanol from that initially present in the reaction mixture is utilized, then a mixed ketal will be formed, i.e., the two Rs in formula II will not be the same. No advantage accrues from using a different alkanol from that initially present, so ordinarily the same alkanol, preferably methanol, will be utilized. The amount of alkanol required to transform the hemi-ketal into the ketal II is 1 mole of alkanol per mole of hemi-ketal. Ordinarily, however, a large excess of alkanol is used since this facilitates further work-up. The ketal forms immediately on contacting of the hemi-ketal with alkanol at ambient temperature in essentially quantitative yield. If excess alkanol is present the ketal will dissolve as it is formed. It can be recovered in crystalline form by chilling the solution of ketal in alkanol below about 0C. and decanting or filtering off the mother liquor. Compound I1 is apparently unique among ketals in that it is stable towards acids but is hydrolyzed by base. This acid stability of the ketal is not only unique but also advantageous since the ketals (II) show fungicidal activity, particularly against rust diseases such as coffee rust, wheat rust, or rice blast. Because of its acid stability, it is therefore compatible with fertilizer formulations, most of which are acidic.

As reported in copending, commonly assigned application Ser. No. 852,881, filed Aug. 25, 1969, now abandoned, the nitro-oximino cycloalkanones (compound Ill) prepared in accordance with the method of the instant invention are also active against plant fungus diseases, in particular against coffee rust disease.

Ketal (II) is transformed into ketone (III) by hydrolysis with 1 mole of base which first forms the enol salt of III and then free ill on neutralization of the enol salt with acid. This transformation is most expeditiously effected by adding to an aqueous suspension of the ketal at least one equivalent of a base such as an alkali or alkaline earth metal oxide or hydroxide, e.g., sodium hydroxide, per mole of ketal at from approximately ambient temperature up to about 50C. Alternatively, the ketal can be added to an aqueous solution containing at least one equivalent of base. As above indicated, the ketal is first transformed into the enol salt by the base. Thereafter, neutralization with any strong, nonoxidizing acid such as for example, HCl forms free compound (lll) plus the acid salt of the base, e.g. in this instance, sodium chloride. Compound lll readily precipitates out of solution and is decanted or filtered off. The salt, e.g. NaCl, remains in the aqueous solution.

Sulfur dioxide is uniquely advantageous as hereinabove enumerated over other possible reaction solvents. In addition to affording compound Ill in high yield, it is nonflammable, inexpensive, and it is a very good solvent for both reactants and products. Additionally, because of its low boiling point, SO can be readily removed at low temperature without the need for provision for vacuum stripping. As heretofore indicated, HCl is the preferred acid catalyst. l-lCl has a comparatively low solubility in SO at atmospheric pressure and a high solubility at pressures above about atmospheres. Therefore, removal ofboth S0 and HCl from the hemi-ketal product after completion .of the reaction is readily accomplished by allowing the reaction mixture to come to atmospheric pressure at a temperature below about -l0C. causing the HCl to flash off and then allowing the temperature to rise to about lOC. causing flash-off of the S0 leaving behind the hemi-ketal product as a residue. This residue can be further reacted without additional purification.

We have found that use of solvents other than liquid SO or concentrations of a-nitrocycloalkanone in SO if less than wt.%, have numerous disadvantages. Using the two step process of the .instant invention, yields of ketone (III) in excess of 90% are obtained. Using more dilute solutions in SO little ketal II is obtained and the predominant product is ketone III, however, the yield of compound III in dilute solution in S0 is comparatively low. Likewise in mono or dialkyl ethers or other conventional reaction solvents, the product of nitrosation is compound (111) with little or no ketal (ll) being formed. However, the yield of compound III is nonetheless significantly lower than that afforded by the two step process of the instant invention. Other known prior art solvents such as alkanols, halogenated hydrocarbons, or acetic acid also afford compound III in very poor yield.

. The invention can be more fully understood by reference to the following examples. All parts are parts by weight unless otherwise expressly noted.

Examples 1 3 are comparative examples showing the yields of product obtainable when S0 is used as a solvent but low concentrations of nitrocyclohexanone reactant in S0 and no added alkanol ROH are utilized so that the hemi-ketal is not the primary reaction product. The highest yield was 68% (Example 2). Example 4 is a close approximation of Example 2, but utilizes the procedure of the instant invention resulting in a much higher yield.

EXAMPLE 1 Approximately 60 cc ofliquid SO was saturated with anhydrous HCl at l5C. and atmospheric pressure. This yielded a solution 0.8 molar in HCl. Three grams of nitrocyclohexanone (0.021 mol) and 1.8 grams (0.03 mol) of methyl nitrate were then added, and the clear red solution which formed kept at l5C. for 3 hours. The S0 and HCl were then stripped off while maintaining the reaction mixture below 0C.,and the residue was recrystallized from a small amount of methanol at approximately lOC. The percentage conversion of nitrocyclohexanone to 2-nitro-6-oximino cyclohexanone was 60 mol percent as determined by vapor phase chromatographic analysis of the reaction mixture for unreacted starting material. The amount of 2-nitro-6-oximino cyclohexanone recovered from the crystallization was 0.64 gram while 0.32 gram was present in the mother liquor. This amounts to a total of 0.96 gram of oximine-nitrocyclohexanone or 44 mol percent based on consumed nitrocyclohexanone starting material.

EXAMPLE 2 A solution of 1.5 grams (10.5 millimols).of nitrocyclohexanone was dissolved in 33 cc of liquid S0 and this solution was then saturated with gaseous HCl at l5C. and approximately 4 atmospheres producing a solution approximately 5 M in HCl. At this point, the

solution was cooled to 80C. and 1.5 grams millimols) of methyl nitrite added. The reaction mixture was brought to reaction temperature of-15C. i 2C. andthis temperature maintained for 4 hours. The S0 and HCl present were removed while maintaining the temperature below 0C., and the residue was recrystallized from a small amount of methanol. 0.713 Gram of pure crystalline 2-nitro6-oximino-cyclohexanone was obtained while 0.482 gram of the same product remained in the filtrate. The amount of desired product amounted to 1.20 gram or 68% based on 2-nitrocyclohexanone consumed. Vapor phase chromatographic analysis showed that at least 99 mol percent of the starting material, nitrocyclohexanone, had been consumed.

EXAMPLE 3 To a solution of 1.5 gram (10.5 millimols) of nitrocyclohexanone in 33 cc liquid S0 which had been saturated with'HCl to give a 4.4 molar solution, was added 1.1 grams (17.0 millimols) of nitrosyl chloride 'while the temperature was maintained at 78C. The mixture was then allowed to warm up to about 15C. and

maintained at this temperature for 3.5 hours. The pres- EXAMPLE 4 A solution of 9.0 grams of nitrocyclohexanone was dissolved in 33 cc of liquid S0 and this solution was then saturated with gaseous HCl atl5C. and approximately 4 atmospheres producing a solution approximately 5 M in HCl. At this point, the solution was cooled to 80C. and 9.0 grams of methyl nitrite and I 4.8 g of CH OH added. The reaction mixture was brought to reaction temperature of l 5C. i 2C. and this temperature maintained for 4 hours. The S0 CH OH and HCl present were then removed while maintaining the temperature below 0C. The crude residue was dissolved in 50 cc of methanol at 35C. and

the solution then cooled to 0C. affording white crystals which were collected by suction filtration. Additional crystals were obtained by adding 50 cc water to the mother liquors. The combined crystals were then shaken for 3 hours at 40C. with 20 cc of 5N. aqueous NaOl-l and the thereby resulting solution then neutralized with 5N HCl affording a white precipitate of 2- nitro-6-oximino cyclohexanone which was collected by suction filtration, washed with distilled water and dried in vacuo. Yieldof product was 9.7 g

EXAMPLES 5 26 The reaction vessel utilized was a glass-lined pressure vessel fitted with a Monel pressure gauge and valve and internal magnetically actuated stirring means. In a typical run, 10 parts of (it-nitrocyclohexanone (hereinafter ANC) were charged to the reaction vessel which was then cooled to 78C. and liquid S0 in the desired quantity fed in. ln those instances where acid catalyst 7 and/or alkanol were being used, they were added to the chilled vessel immediately after the S Finally, the nitrosating agent was added. The vessel was sealed and warmed to the desired reaction temperature where it 8 to 6.5 g (I00 mmole) ethylene glycol, which contained 0.10 g (2.5 mmole) of dry sodium hydroxide. The mixture was heated to 70C. and maintained at this temperature for 1 hour while a slow stream of nitrogen was was maintained for V2 t0 12 h0l1f$- The reaction bubbled through it in order to remove methanol. Then ture was then vacuum stripped on a rotary evaporator the reaction mixture was cooled to 5C. and ml of at l5 C. affording hemi-ketal. Then 100 parts of Cold cold 0.33 N hydrochloric acid (5 mmole) was added in methanol was added to the evaporation resldue resultone shot with good stirring. White crystals precipitated mg in the format1on of white crystals of the ketal (comwhich were filtered after standing for ten minutes and pound II) which were collected by filtration and 10 then washed with ml of cold water. Yield 2.11 g of washed with cold methanol. Additional ketal crystals NOC-ethylene ketal, m.p. l88192C. (97% 0f thewere obtained by adding an equal volume of water to ory). GLC analysis [after silylization] showed no unrethe mother liquor and cooling. Yields given in the table acted NOC-dimethyl ketal in the product or in the below are for the combined crops of ketal crystals. The mother liquor. The melting point of the product did not combined crystals were dissolved 1n 50 parts of 2N 15 change after recrystallization from methanol/water aqueous alkali at about C. After brief standing at (88% recovery). this temperature, this reaction mixture was neutralized by pouring into parts of cold 2N HCl resulting in the The ketal (compound II) can, of course, have its R immediate formation of pale yellow crystals of comgroups exchanged by other mono ordihydroxy alcohols pound III. These crystals were collected by suction 20 in addition to ethylene glycol. Essentially any mono or filtration, washed with cold water, dried in vacuo and dihydroxy alcohol having a boiling point greater than the yield thereof determined. Evaporation of the methanol can replace CH as the R groups in commother liquor afforded essentially no additional prod pound III. Suitable mono hydroxy alcohols include the uct. The yield of compound III was in all cases approxi- C to C alkanols and the C to C alicyclic alcohols. mately 96% of the yield of ketal. 25 Suitable glycols include a,,B-dihydroxy cycloalkanes Results for the above series of experiments are tabuhaving at least 5 carbons and vicinal-dihydroxy alkanes lated below. from C to C The ketal would then have the formula Nitrosating Moles Parts Moles Nitrosation Agent and HCl/ MeOHl Reaction Yield Moles There- Moles Parts Mole Temp. C. of Example of/Mole ANC ANC ANC ANC and Time Ketal 5 meONO, L25 6.0 4.0 1.0 l5, 1 hr. 93 6 MeONO, 1.5 6.0 4.0 1.0 15. 1 hr. 94 7 MeONO, 2.5 6.0 4.0 1.0 -l5. 1 hr. 93 8 MeONO, 1.0 6.0 4.0 1.0 15, 1 hr. 9 NOCI, 1.5 6.0 4.0 10 15. 1 hr. 86 10 NOCI, 1.5 6.0 4.0 0 15, 1 hr. 0 11 NOCI, 1.5 6.0 4.0 2.0 -15". 1 hr. 89 12 NOCl. 1.0 6.0 4.0 2.0 15. 1 hr. 84 13 N 0 1.5 6.0 4.0 1.0 15, 1 hr. 74 14 MeONO 1.5 2.0 4.0 1.0 15. 1 hr. 0 l5 MeONO. 1.5 3.0 4.0 1.0 -15", 1 hr. 40 16 MeONO. 1.5 5.0 4.0 1.0 15. 1 hr. 87 17 MeONO. 1.5 10.0 4.0 10 15, 1 hr. 93 18 MeONO, 1.5 6.0 2.0 1.0 15. 1 hr. 69 19 MeONO. 1.5 6.0 3.0 1.0 15, 1 hr. 91 20 MeONO, 1.5 6.0 4.0 0 l5, 1 hr. 80 21 MeONO, 2.0 6.0 4.0 0 15 1 hr. 92 22 MeONO. 1.5 6.0 4.0 0.5 15. 1 hr. 92 23 MeONO. 1.5 6.0 4.0 2.0 15, 1 hr. 93 24 MeONO, 1.5 6.0 4.0 15* 15, 1 hr. 25 MeONO, 1.5 6.0 4.0 1.5 0, 0.5 hr. 26 MeONO, 1.5 6.0 4. 1.5 30. 4 hr. 90

i-PrOH used insmad of methanol and mixed hemi-kelalohu1ined.i.e.par1ofR was Me from MeONO and part i-Pr from i-PrOH.

EXAMPLE 27 EXAMPLE 28 Alcoholysis of NOC-Dimethyl Ketal NOC-dimethyl ketal, 2.19 g (10 mmole) was added R-;\ R1 (IIHPCH O O HON=C CHNO: :CHoH

wherein R and R can be hydrogen, or an alkyl group of up to 10 carbons with R plus R having a total of l to 10 carbons when alcoholysis is effected using an a-B-dihydroxy alkanc, and the formula 9 4 2), f. neutralizing said enol salt.

H 2. A process in accordance with claim 1 wherein the i i alkan'ol of steps (b) and (d) is methanol.

5 3. A process in accordance with claim 1 wherein the HON=C H CHNO concentration of a-nitroketone in S0 ranges from about to about 35 wt.%.

4. A' process in accordance with claim 1 wherein said wherein X is at least 3 when using a-B-dihydroxy cyclonitrosating agent is a 1 to 4 alkyl nitrite and there is alkane 10 present at least 0.5 mole of C to C alkanol per mole of We claim: a-nitroketone. l. A process for the preparation of a compound f 5. A process in accordance with claim 4 wherein said the structure; I nitrosating agent is methyl nitrite.

6. A process in accordance with claim 4 wherein said alkanol is methanol.

0 l /|K 5 7. A process in accordance with claim 1 wherein n 3. 8.Aprocess in accordance with claim 1 wherein said (CH temperature ranges from about C. up to about +5C. 20 9 A rocess com risin the ste sof' wherein n is an integer ranging from 2 to 9 comprising p p g p the Steps of: a. forming an at least 10 wt.% solution of an aa. forming an at least 10 wt.% solution of an amtroketone of the structure:

nitroketone of the structure: I

I 0 2K CH2/\/CHNO2 CH ciiNo HZL.

wherein n 18 an integer ranging from 2 to 9 in liquid S0 wherein as f above m quid S02; b admixing with said solution at a temperature rangb. admixing with said'solution at a temperature ranging from about to at least about 1 mg from about to +25%" at least about mole per mole of said a-nitroketone of a nitrosatmole per mole of said a-nitroketone of a nitrosatm agent Selected from the group consisting f C1 ing agent Selected from the group Consisting of C1 to C alkyl nitrites, N 0 nitrosyl formate, nitrosyl to C4 alkyl mites, 2 3 nitrosyl nitrosyi chloride and nitrosyl bromide and when said nichloride and nitrosyl bromide and when said nitrosating agent is N203, nitrosyl f t nitrosyl trosating agent is 2 3 nitrosyl formate, rflimsyx chloride or nitrosyl bromide, at least 1.0 mole of an 'chloride or nitrosyl bromide, at least 1.0 mole of an 40 k l OH per l f Obnitroketone h i R alkanol ROH per mole of a-nitroketone wherein R is a CI to C4 aiky] group, and at least about 40 is 1 to 4 alkyl p and at least about moles of a strong acid per mole of said a-nitrokemoles of a strong acid per mole of said a-nitroketone; tone; c. separating from the thereby formed hemi-ketal c. separating from the thereby form hemi-ketal reaction product from said sulfur dioxide, acid, any

reaction product sulfur dioxide, acid, and any unre unreacted nitrosating agent and alkanol; and acted nitrosating agent and alkanol; d. reacting said reaction product with at least about (1. reacting said reaction product with at least about 1.0 mole of an alkanol ROH per mole of reaction 1.0 mole of an alkanol ROH per mole of reaction product to thereby afford a ketal of the structure: product to thereby afford a ketal of the structure:

' RO OR RO\C/OR \C/ HON=C CHNO, HON=C/ \CHNO2 (CH2)" (Ci l2) wherein R and n are as defined above; wherein R and n are as defined above.

c. reacting said ketal with at least one equivalent of base to afford an enol salt; and 

1. A PROCESS FOR THE PREPARATION OF A COMPOUND OF THE STRUCTURE:
 2. A process in accordance with claim 1 wherein the alkanol of steps (b) and (d) is methanol.
 3. A process in accordance with claim 1 wherein the concentration of Alpha -nitroketone in SO2 ranges from about 15 to about 35 wt.%.
 4. A process in accordance with claim 1 wherein said nitrosating agent is a C1 to C4 alkyl nitrite and there is present at least 0.5 mole of C1 to C4 alkanol per mole of Alpha -nitroketone.
 5. A process in accordance with claim 4 wherein said nitrosating agent is methyl nitrite.
 6. A process in accordance with claim 4 wherein said alkanol is methanol.
 7. A process in accordance with claim 1 wherein n
 3. 8. A process in accordance with claim 1 wherein said temperature ranges from about -20*C. up to about +5*C.
 9. A process comprising the steps of: a. forming an at least 10 wt.% solution of an Alpha -nitroketone of the structure: 